<html>
	<head>
		<meta charset="utf-8" />
		<title></title>
	</head>
	<body>
		<input type="text" placeholder="半径" id="c"/>
		<input type="text" placeholder="周长" id="a"/>
		<input type="text" placeholder="面积" id="o"/>
		<script>
			 
			var p=Math.PI;
			console.log(p);
			
			
			var t=prompt("输入圆的半径")
			t=Number(t);
			
			var n=t*2*p;
			var g=t*t*p;
			
			document.querySelector("#c").value=t;
			document.querySelector("#a").value=n;
			document.querySelector("#o").value=g;
			
		</script>
	</body>
</html>
